In 1943, the federal Crown used its sovereign power of expropriation to divest Gordon Edwards of his title to the house, in order to consolidate public ownership of the lands along the Ottawa River. Edwards had fought the action, but eventually lost the dispute with the Canadian government in 1946 and died at the house later that year.[1] After several years of uncertainty, in 1950 the government decided to refurbish the property as a residence for the prime minister, with Louis St. Laurent becoming the first to take up residence there in 1951. Except for Kim Campbell, every prime minister since that date has resided at 24 Sussex Drive for the duration of their mandates; previous prime ministers lived at a variety of locations around Ottawa: Sir Wilfrid Laurier and William Lyon Mackenzie King, for instance, lived at Laurier House in Sandy Hill when they were prime minister. Laurier House was willed to the Crown upon Mackenzie King's death in 1950 and was thus also available for designation as the prime minister's official residence at the time.

Security at 24 Sussex was overhauled following a November 1995 attempted assassination by André Dallaire, who wandered around the house and grounds for nearly an hour before being confronted outside Jean Chrétien's bedroom by the Prime Minister's wife, Aline; she locked the door to the bedroom while Chrétien guarded it with an Inuit stone carving. Ultimately, Royal Canadian Mounted Police officers arrested Dallaire. Measures put in place after the attempted assassination include the addition of several more guards to the house's attache, the installation of crash-proof barriers within the main gates, and the addition of several more security cameras.[2]

Despite the building not having any bureaucratic function, it has been the location of protests, such as when farmers drove their tractors in a convoy past the front of the property in 2006,[3] and when Greenpeace activists chained themselves to the front gates in March 2007.[4]

One consequence of the building's lack of official bureaucratic functions is that unlike examples such as 10 Downing Street, the White House and even Rideau Hall, 24 Sussex Drive has never been widely used as a metonym for the Office of the Prime Minister - this is referred to simply as the "Prime Minister's Office," which is often abbreviated as "PMO."

The residence is spread on four floors, from the basement to the third floor. The basement consists of support rooms, including the laundry room. The main floor of the residence includes the dining room, which is used for both official and unofficial dinners, the living room, the kitchen, which is staffed by a head chef and support staff, the main stair hall, the prime minister's library, and a sun room. The second floor is primarily bedrooms, including the master bedroom, as well as the office of prime minister's spouse. The third floor contains additional bedrooms, and a private study for the prime minister.

The National Capital Commission maintains a selection of historic furnishings from the Crown Collection for use in the public rooms of the mansion, ranging from musical instruments to chairs and tables to paintings by famous Canadians. Due to the lack of restraints on the prime minister of the day to do what he/she pleases with the mansion, several prime ministers have left their own marks on the building; for example, unnamed business associates of Pierre Trudeau installed a swimming pool for his frequent workouts. The pool reportedly cost C$275,000 due to an underground access increasing the expense. This was raised in a "public fund" headed by Keith Davey. The donors to this fund were never made public.[6][7]

Being the first to publicly reveal the renovation costs, the high tab for Brian and Mila Mulroney's changes to the building caused political controversy, especially when some of the costs were paid for from the PC Canada Fund, which raised money from individual donations to fund the Progressive Conservative Party.

24 Sussex Drive, front view in winter

Since then, very little has been spent on renovating the building, leaving parts of it somewhat tattered and outdated. Most notable is the leopard spot carpet Mila Mulroney put on the staircase, which was only recently removed by the current occupants, Stephen Harper and his family. The house lacks central air conditioning, and is cooled by a series of window-mounted air conditioners. In November 2004, Prime Minister Paul Martin complained about the house's heating system. According to his statement, the century-old house gets "too cold in the winter and too hot in the summer." Harper moved in on February 9, 2006, and has said he may move out temporarily during a future summer, so that renovations may be done.

On May 6, 2008, the Auditor General reported that the house is in poor condition and needs about C$10 million in repairs and upgrades, which would require at least 12 to 15 months of "full access" to complete.[8]